This invention relates to welding, and more particularly to an apparatus and method for twisting two or more strands of welding wire prior to use thereof in a welding operation.
In a welding application, it is known to use a consumable electrode made of a plurality of intertwisted wire strands, such as is disclosed in U.S. Pat. No. 4,386,259 to Nagai, et al. This patent, along with other known processes, involves use of a multiple strand electrode which is intertwisted off-line. The twisted electrode or wire allows a wider weld bead than would otherwise be possible with a single-strand electrode or wire.
The present invention provides an apparatus and method for in-line twisting of strands of welding wire, immediately upstream of the welding torch head which performs the welding operation. In accordance with the invention, a welding wire feeder for positioning upstream of a welding torch head includes a housing having an inlet for receiving the strands of wire, and advancing means for advancing the wire through the housing. Twisting means is associated with the housing downstream of the inlet and upstream of the head for imparting twisting to two or more strands of wire as they are advanced through the housing, thereby providing a twisted multi-strand element for use in welding. In a preferred embodiment, the advancing means is provided on a rotatable member mounted to the housing, and the twisting means causes rotation of the rotatable member about a longitudinal twisting axis substantially parallel to the direction of advancement of the wire through the housing. The rotatable element preferably comprises a spindle member having an interior cavity formed at one end thereof, with the cavity being in communication with the housing inlet and the advancing means disposed within the spindle cavity. In this manner, upon simultaneous operation of the advancing means and rotation of the spindle member, twisting is imparted to the strands of wire due to rotation of the advancing means about the twisting axis. The advancing means preferably comprises a pair of wire feed rollers rotatably mounted within the spindle member cavity. Drive means is provided for imparting rotation to the wire feed rollers. The drive means preferably comprises a rotatable inner gear located in the spindle member cavity, and drivingly engaged with one of the wire feed rollers. An outer gear located on the exterior of the spindle member is drivingly connected to the inner gear. A drive gear assembly is rotatably mounted to the exterior of a portion of the spindle member downstream of the cavity, at least a portion of which is engageable with the outer gear. In one embodiment, the drive gear assembly is interconnected to a drive motor through a worm wheel and worm gear arrangement, for rotating the drive gear assembly about the spindle member. Such rotation of the drive gear assembly causes rotation of the outer gear, which imparts rotation to the inner gear and thereby drives the wire feed rollers. A twisting motor is preferably connected to the housing, and is interconnected with the spindle member through a pulley and timing belt arrangement. In this manner, upon selective actuation of the twisting motor, the spindle member is rotated about the twisting axis for imparting rotation to the wire feed rollers. A passage is formed in the spindle member downstream of the cavity for receiving the twisted wire, and includes an outlet for feeding the twisted wire to the welding torch head.
The invention also contemplates a method of twisting welding wire, substantially in accordance with the foregoing description.